The information is presented in Table D1. The data
were recorded as the number of samples that exceeded
0.1 mg l-1,
with no further information available on the highest
concentrations reported.EQS exceedences
were only seen infrequently with 6 sites (less than
2%) breaching relevant standards. Two EQS failures
were reported for:

Metal concentrations in estuaries were higher than
at intermediate and offshore sites. This is interpreted
as being a direct consequence of the proximity of
estuarine sites to inputs, e.g. rivers. Within estuaries,
there was also a general tendency for metal concentrations
to decrease with increasing salinity. Where information
is available, concentrations tended to be higher
in those estuaries receiving inputs from industrial
and/or domestic sources. Examples are cadmium (Severn),
chromium (CIyde), lead (Tyne, Tees and Thames) and
zinc (Tyne, Wear and Mersey).

Relative to metal concentrations in estuaries,
those observed at intermediate and offshore sites
were low and consequently of no real concern as
regards compliance with EQSs. The data do, however,
reveal some features of interest. Many of the metals
included in the survey show higher concentrations
in the southern rather than in the northern North
Sea. This was attributed to the generally lower
salinity in the southern North Sea, a consequence
of the greater freshwater input from major rivers.
A similar effect is evident for parts of the Irish
Sea, where apparently high concentrations of metals
can be attributed to the lower salinity of this
area (CEFAS, 1997). Some metals are extremely particle-reactive,
tending to be adsorbed onto suspended particles,
with a consequent reduction in the dissolved phase
concentration. Relatively high dissolved lead concentrations
in the vicinity of Dogger Bank, observed in this
and in other studies (Laslett, 1995), are attributed
to the relatively clear waters of this area, where
there is little removal onto particles.

However, with the exception of HCH, atrazine, simazine,
chloroform, carbon tetrachloride, trichloroethylene,
tetrachloroethylene, trichloroethane and PCP, the
compounds were found at concentrations below analytical
limits of detection. Insufficient positive results
were available for analysis and therefore these
data were not presented in the NMP report. However,
the detection limits used are generally well below
the EQS concentrations, indicating low background
concentrations in UK marine waters.

Gamma-HCH (lindane)

Median concentrations of HCH were below the EQS
concentration of 20 ng l-1 at all sites
except the Thames at Woolwich. Individual results
above EQS were found on the Tay, Ouse, Thames, Tamar,
Mersey and Clyde. These elevated results were found
in estuaries with either riverine sources (Ouse,
Thames and Mersey) or in the vicinity of major urban
conurbations which, in some cases, have known discharges
(e.g. sewage discharges in the Thames and the combined
effects of sewage and industrial discharges to the
Clyde).

Generally, concentrations decline moving offshore,
although concentrations in the outer Thames estuary
off the East Anglian coast and south-eastern Irish
Sea are higher than in the English Channel and Irish
Sea off Northern Ireland. This may be due to transport
of gamma-HCH on suspended particulate material.

Atrazine and Simazine

The NMP stated that no atrazine and simazine data
were available for sites in Scotland, Northern Ireland
or offshore sites.

All results for atrazine and simazine were significantly
lower than the proposed EQS concentrations (statutory
EQS of 2 mg l-1
(annual average) and a non-statutory EQS of 10mg l-1
(maximum allowable concentration) as the sum of
atrazine and simazine). The highest median concentrations
of atrazine and simazine were found in the Humber
and Ouse estuaries respectively. Elevated concentrations
were also found in the Thames, Tamar, Severn and
Mersey, all of which have riverine sources. The
ratio of atrazine to simazine was found to vary
from estuary to estuary, probably because of variations
in rates of application of these herbicides in the
catchments.

Concentrations of atrazine and simazine found in
this survey are comparable with earlier surveys
(MAFF 1993, 1994). However, concentrations found
in the NMP survey in the Thames, Tamar and Mersey
are at the lower end of the range reported by Evans
et al (1993) for surveys carried out in 1991
and 1992. This may be due to reductions in inputs
of triazine herbicides to the marine environment
resulting from the ban on non-agricultural use during
the first year of the NMP survey. Evans et al
(1993) stated that peak concentrations were found
during periods of highest pesticides use or after
rainfall. The timing of the surveys is likely to
substantially affect observed estuarine concentrations.

Chloroform

Of the 44 sites with results available, 13
had results in which all values were below the detection
limit. Median concentrations of chloroform were
below the EQS of 12mg l-1 at all sites. Only one result
(inthe Wear estuary) was greater than the
EQS. Elevated concentrations were also observed
in the Tees and Mersey estuaries, which receive
point source discharges of chloroform. The apparent
elevated concentrations of chloroform in the Thames
estuary, Solway Firth and off the Lune estuary are
a consequence of relatively high limits of detection.

Carbon tetrachloride

Of the 44 sites with results available, 24 sites
had results in which all values were below the limits
of detection. Median concentrations of carbontetrachloride at all sites were almost one tenth
of the EQS concentration of 12 mg l-1.
Only one result, for a sample collected in the Wear,
approached the EQS concentration. However, all North
Sea states were obliged to discontinue production,
consumption and import by 1 January 1996.

Trichloroethylene

Of the 30 sites with results available, 18 sites
had results where all values were below the limits
of detection. Median concentrations of trichloroethylene
were all below the EQS of 10 mg l-1.
The highest individual concentration was found in
the Wear estuary, which receives inputs of trichloroethylene
from both river and point source discharges. Positive
results were also recorded in the Severn and Mersey
estuaries, which receive inputs of trichloroethylene
from point source discharges and riverine sources.

Tetrachloroethylene

Of the 29 sites with results available, 18 had
results in which all values were below limits of
detection. All results were at most one tenth of
the EQS concentration of 10 mg l-1. The highest median concentration
was found in the Wear estuary which receives inputs
of tetrachloroethylene. Positive results were recorded
in the Humber, Severn and Mersey estuaries, all
of which have point sources.

Trichloroethane

Of the 37 sites surveyed, 18 had results in which
all values were below the limit of detection. All
results were substantially below the proposed EQS
of 100 mg l-1 (annual average) for 1,1,1,
trichloroethane. Positive results were recorded
in the Tees, Severn and Mersey estuaries which receive
inputs of trichloroethane from industrial point
source discharges.

Pentachlorophenol (PCP)

The EQS for PCP is 2,000 ng l-1. Of
the 41 sites with results available, 29 had results
in which all values were below the limit of detection.
Median results at all sites were at most one tenth
of the EQS. The NMP survey found it difficult to
comment on spatial variability of PCP because few
results above the limit of detection were recorded.

PAHs

The 10 PAH compounds for which data were considered
within this assessment are a subset of those determined.
The full data are presented elsewhere (Law et
al 1997a).

The highest concentrations generally occur in major
estuaries, particularly those of the Humber, Great
Ouse, Thames and Tees. PAH concentrations at offshore
sites were generally low or undetectable. Of the
39 samples taken at offshore locations (10 miles
or more from the coast), only one (NMP station 245
off the River Tyne sampled in 1993) showed a significant
concentration of PAH, and this was only for naphthalene
(263 ng l-1). Apart from this sample,
PAHs were generally not detected inoffshore
waters. Higher concentrations were found in coastal
and estuarine samples (although not in all), with
total PAH concentrations ranging from none detected
to 8.5 mg l-1.
Total PAH concentrations greater than 1 mg l-1
were found at 14 sites, in the estuaries of the
Rivers Tees, Humber, Great Ouse, and Thames.
Of these 14 sites, 10 were in the lower reaches
of the River Tees estuary, and particularly high
concentrations were observed in the vicinity of
Redcar Jetty. The PAH profile observed in the five
samples collected off Redcar Jetty was dominated
by two- and three-ring PAHs, probably derived from
an adjacent steel plant. The other data probably
reflect inputs from a wide range of combustion processes,
involving both industrial and domestic sources.

Comparison of samples for which duplicate filtered/
unfiltered concentrations were determined indicated
that, for the lower molecular weight PAHs, the major
portion was present in the dissolved phase (e.g.samples from the River Tees), while for thehigher molecular weight PAHs the major portion
was adsorbed onto particles.

While investigation in the NMP survey was only
considered a 'pilot'
study, the results obtained suggested that concentrations
were low or undetectable at intermediate and offshore
sites. However, significant concentrations of PAH
have been found in a number of estuaries.